It is known that the performance of lithium secondary batteries becomes degraded when they are used in a high-voltage region or a low-voltage region. Therefore, lithium secondary batteries are generally used in a voltage range not including cell voltages that cause performance degradation (e.g., a voltage range with which single-cell voltages become higher than or equal to 2.2 V and lower than or equal to 4.2 V).
Furthermore, in the case of lithium secondary batteries that use a manganese-based cathode material, cell degradation occurs considerably at high temperatures, for example, it has been proposed that the batteries be used in a voltage range close to the high-voltage region at high temperatures (e.g., Patent Citation 1).
Furthermore, in consideration of safety, lithium secondary batteries are stored in an intermediate state of charge (e.g., an open-circuit voltage (single-cell voltage with no current flowing) in a range of 3.5 V to 3.8 V) or in a discharged state (e.g., an open-circuit voltage of 3.5 V or lower).    Patent Citation 1: Japanese Unexamined Patent Application, Publication No. 2000-058134